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<head><meta charset="utf-8"><title>I-prioritize #68010 Large ZST arrays take a looong time to c · t-compiler/wg-prioritization · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/index.html">t-compiler/wg-prioritization</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html">I-prioritize #68010 Large ZST arrays take a looong time to c</a></h3>

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<a name="198282113"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198282113" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> triagebot <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198282113">(May 21 2020 at 03:14)</a>:</h4>
<p><span class="user-group-mention" data-user-group-id="2403">@WG-prioritization</span> issue <a href="https://github.com/rust-lang/rust/issues/68010">#68010</a> has been requested for prioritization.</p>



<a name="198288957"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198288957" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198288957">(May 21 2020 at 05:51)</a>:</h4>
<p>Afaict there isn't really a reason to use this and it was undetected for 10 version, <code>P-low</code>?</p>



<a name="198318337"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198318337" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198318337">(May 21 2020 at 13:10)</a>:</h4>
<p>Mhh, I think it's worth bisecting a bit</p>



<a name="198318393"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198318393" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198318393">(May 21 2020 at 13:10)</a>:</h4>
<p>Can we profile the compiler to see where that additional comilation time comes from?</p>



<a name="198353738"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198353738" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198353738">(May 21 2020 at 17:53)</a>:</h4>
<p>Did some bisection, this seems like a const-eval bug. I pinged RalfJung on the issue</p>



<a name="198353880"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198353880" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198353880">(May 21 2020 at 17:54)</a>:</h4>
<p>Depending on his answer I think we can assign <code>P-medium</code> or <code>P-low</code></p>



<a name="198380995"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198380995" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198380995">(May 21 2020 at 21:43)</a>:</h4>
<p><span class="user-mention silent" data-user-id="120791">RalfJ</span> <a href="https://github.com/rust-lang/rust/issues/68010#issuecomment-632358379">said</a>:</p>
<blockquote>
<p>Okay so this is interning walking every single field of that array... and taking forever to do that, obviously.</p>
</blockquote>
<p>So the problem comes from the big size of the array. I think this means we can tag <code>P-low</code>?</p>



<a name="198381523"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198381523" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198381523">(May 21 2020 at 21:47)</a>:</h4>
<p>1.31.0 is the introduction of const evaluation, right? So this isn't much of a regression, but rather a cost induced by const evaluation.</p>



<a name="198384624"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198384624" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198384624">(May 21 2020 at 22:20)</a>:</h4>
<p><span class="user-mention" data-user-id="255061">@LeSeulArtichaut</span> do you want to go ahead and tag <code>P-low</code> and remove <code>I-prioritize</code>?</p>



<a name="198384661"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198384661" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Léo Lanteri Thauvin <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198384661">(May 21 2020 at 22:21)</a>:</h4>
<p>Ok</p>



<a name="198384785"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2368010%20Large%20ZST%20arrays%20take%20a%20looong%20time%20to%20c/near/198384785" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> triagebot <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2368010.20Large.20ZST.20arrays.20take.20a.20looong.20time.20to.20c.html#198384785">(May 21 2020 at 22:22)</a>:</h4>
<p>Issue <a href="https://github.com/rust-lang/rust/issues/68010">#68010</a>'s prioritization request has been removed.</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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